/* * Copyright (c) 2011 Smartjog S.A.S, Clément Bœsch * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file * Potential thumbnail lookup filter to reduce the risk of an inappropriate * selection (such as a black frame) we could get with an absolute seek. * * Simplified version of algorithm by Vadim Zaliva . * @see http://notbrainsurgery.livejournal.com/29773.html */ #include "libavutil/opt.h" #include "avfilter.h" #include "internal.h" #define HIST_SIZE (3*256) struct thumb_frame { AVFrame *buf; ///< cached frame int histogram[HIST_SIZE]; ///< RGB color distribution histogram of the frame }; typedef struct ThumbContext { const AVClass *class; int n; ///< current frame int n_frames; ///< number of frames for analysis struct thumb_frame *frames; ///< the n_frames frames AVRational tb; ///< copy of the input timebase to ease access } ThumbContext; #define OFFSET(x) offsetof(ThumbContext, x) #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM static const AVOption thumbnail_options[] = { { "n", "set the frames batch size", OFFSET(n_frames), AV_OPT_TYPE_INT, {.i64=100}, 2, INT_MAX, FLAGS }, { NULL } }; AVFILTER_DEFINE_CLASS(thumbnail); static av_cold int init(AVFilterContext *ctx) { ThumbContext *s = ctx->priv; s->frames = av_calloc(s->n_frames, sizeof(*s->frames)); if (!s->frames) { av_log(ctx, AV_LOG_ERROR, "Allocation failure, try to lower the number of frames\n"); return AVERROR(ENOMEM); } av_log(ctx, AV_LOG_VERBOSE, "batch size: %d frames\n", s->n_frames); return 0; } /** * @brief Compute Sum-square deviation to estimate "closeness". * @param hist color distribution histogram * @param median average color distribution histogram * @return sum of squared errors */ static double frame_sum_square_err(const int *hist, const double *median) { int i; double err, sum_sq_err = 0; for (i = 0; i < HIST_SIZE; i++) { err = median[i] - (double)hist[i]; sum_sq_err += err*err; } return sum_sq_err; } static AVFrame *get_best_frame(AVFilterContext *ctx) { AVFrame *picref; ThumbContext *s = ctx->priv; int i, j, best_frame_idx = 0; int nb_frames = s->n; double avg_hist[HIST_SIZE] = {0}, sq_err, min_sq_err = -1; // average histogram of the N frames for (j = 0; j < FF_ARRAY_ELEMS(avg_hist); j++) { for (i = 0; i < nb_frames; i++) avg_hist[j] += (double)s->frames[i].histogram[j]; avg_hist[j] /= nb_frames; } // find the frame closer to the average using the sum of squared errors for (i = 0; i < nb_frames; i++) { sq_err = frame_sum_square_err(s->frames[i].histogram, avg_hist); if (i == 0 || sq_err < min_sq_err) best_frame_idx = i, min_sq_err = sq_err; } // free and reset everything (except the best frame buffer) for (i = 0; i < nb_frames; i++) { memset(s->frames[i].histogram, 0, sizeof(s->frames[i].histogram)); if (i != best_frame_idx) av_frame_free(&s->frames[i].buf); } s->n = 0; // raise the chosen one picref = s->frames[best_frame_idx].buf; av_log(ctx, AV_LOG_INFO, "frame id #%d (pts_time=%f) selected " "from a set of %d images\n", best_frame_idx, picref->pts * av_q2d(s->tb), nb_frames); s->frames[best_frame_idx].buf = NULL; return picref; } static int filter_frame(AVFilterLink *inlink, AVFrame *frame) { int i, j; AVFilterContext *ctx = inlink->dst; ThumbContext *s = ctx->priv; AVFilterLink *outlink = ctx->outputs[0]; int *hist = s->frames[s->n].histogram; const uint8_t *p = frame->data[0]; // keep a reference of each frame s->frames[s->n].buf = frame; // update current frame RGB histogram for (j = 0; j < inlink->h; j++) { for (i = 0; i < inlink->w; i++) { hist[0*256 + p[i*3 ]]++; hist[1*256 + p[i*3 + 1]]++; hist[2*256 + p[i*3 + 2]]++; } p += frame->linesize[0]; } // no selection until the buffer of N frames is filled up s->n++; if (s->n < s->n_frames) return 0; return ff_filter_frame(outlink, get_best_frame(ctx)); } static av_cold void uninit(AVFilterContext *ctx) { int i; ThumbContext *s = ctx->priv; for (i = 0; i < s->n_frames && s->frames[i].buf; i++) av_frame_free(&s->frames[i].buf); av_freep(&s->frames); } static int request_frame(AVFilterLink *link) { AVFilterContext *ctx = link->src; ThumbContext *s = ctx->priv; int ret = ff_request_frame(ctx->inputs[0]); if (ret == AVERROR_EOF && s->n) { ret = ff_filter_frame(link, get_best_frame(ctx)); if (ret < 0) return ret; ret = AVERROR_EOF; } if (ret < 0) return ret; return 0; } static int config_props(AVFilterLink *inlink) { AVFilterContext *ctx = inlink->dst; ThumbContext *s = ctx->priv; s->tb = inlink->time_base; return 0; } static int query_formats(AVFilterContext *ctx) { static const enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_RGB24, AV_PIX_FMT_BGR24, AV_PIX_FMT_NONE }; AVFilterFormats *fmts_list = ff_make_format_list(pix_fmts); if (!fmts_list) return AVERROR(ENOMEM); return ff_set_common_formats(ctx, fmts_list); } static const AVFilterPad thumbnail_inputs[] = { { .name = "default", .type = AVMEDIA_TYPE_VIDEO, .config_props = config_props, .filter_frame = filter_frame, }, { NULL } }; static const AVFilterPad thumbnail_outputs[] = { { .name = "default", .type = AVMEDIA_TYPE_VIDEO, .request_frame = request_frame, }, { NULL } }; AVFilter ff_vf_thumbnail = { .name = "thumbnail", .description = NULL_IF_CONFIG_SMALL("Select the most representative frame in a given sequence of consecutive frames."), .priv_size = sizeof(ThumbContext), .init = init, .uninit = uninit, .query_formats = query_formats, .inputs = thumbnail_inputs, .outputs = thumbnail_outputs, .priv_class = &thumbnail_class, };